Neutron generators are used in oil and gas field tools for a variety of different applications. Neutron generators use electronic neutron sources to generate neutrons. In some cases, neutron generators are used as alternatives to chemical neutron sources. Electronic neutron generators have several advantages over chemical neutron sources. For example, electronic neutron generators can be switched on and off, have higher neutron output, and have the capability of pulsed operation.
To generate neutrons, electronic neutron generators use an ion source, an accelerating structure, and a target. In conventional neutron generators, the ion source includes a cathode. The cathode is brought to high temperature so that it emits electrons. The electrons are then used to ionize a gas. The gaseous ions are accelerated by the accelerating structure towards the target. When the ions strike the target, neutrons are produced through nuclear reactions, such as the following fusion reaction: 3H+2H=n+4He+14.1 MeV.
Such conventional “hot cathode” ion sources, however, are difficult to use in oil and gas field tools because they require operation at very high temperatures. Accordingly, hot cathode ion sources have high power requirements. Furthermore, problems with high temperature operation are compounded because neutron generators can use electrical insulation, which impedes heat flow and magnifies high temperatures within the neutron generator. In one example, insulation is used to insulate a high voltage system that powers the accelerator. Such magnified high temperatures can adversely affect the performance and lifetimes of components within the neutron generator.